The present invention relates to telecommunication systems. In particular, the invention concerns a new type of method and system for updating an encryption key in a telephone exchange system.
A telephone network traditionally consists of a plurality of separate telephone exchanges connected to each other via transmission lines. Further, subscribers are connected to telephone exchanges via various subscriber interfaces. An example of the telephone exchange is the DX 200 switching center manufactured by Nokia.
In the DX 200 switching system and in the associated user interface (Man Machine Interface, MMI), the authority and rights of a user who can e.g. give control commands to the various computer units in the switching center are determined on the basis of a user identification (User ID). For each user ID, an individual password for the authentication of the user has been defined. For the minimization of data security risks, it is necessary that the password be changed frequently enough to ensure that a person not authorized to use a user ID will not be able to utilize a user ID that does not belong to him/her. The password is generally stored in an encrypted form. In addition, the password can be assigned a maximum validity period.
To achieve a sufficient level of data security, the user must change his/her password from time to time. Data security can be further improved by regularly changing the encryption key used for the encryption of passwords in the system. However, changing the encryption key involves a problem. When the person maintaining the system changes the encryption key to be used in the system, he/she must change his/her own password at the same time. When the encryption key is changed, all passwords in the system become invalid. The passwords become invalid because they have been encrypted using an asymmetric encryption algorithm. The term xe2x80x98asymmetricxe2x80x99 means that it is not possible to restore the plain-language form of the password from its encrypted form. In this situation, the maintainer is the only person who has an encrypted password consistent with the new encryption key. This means that the maintainer would have to change the passwords of all users in conjunction with the introduction of a new encryption key.
The object of the present invention is to eliminate the drawbacks referred to above or at least to significantly alleviate them.
A specific object of the invention is to disclose a new type of method and system which will allow the updating of an encryption key used in a telephone exchange system to be automated while at the same time making the change of the encryption key used invisible to the users.
As for the features characteristic of the present invention, reference is made to the claims.
The present invention concerns a method for updating the encryption key used for the encryption of a password in a telephone exchange system. The telephone exchange system comprises a telephone exchange, a maintenance center connected to the telephone exchange, a first database, which contains user-specific information, and a second database, which contains the encryption methods used in the telephone exchange system as well as the information and/or encryption keys associated with them. In addition, the first and second databases are connected to the maintenance center. The function of the maintenance center is to manage and monitor the operation of the network elements connected to it. The maintenance center may be a separate physical element or e.g. a logical functional unit physically integrated with another element.
In the method, data indicating, firstly, the encryption key last used in the telephone exchange system and, secondly, the password encrypted with this encryption key is written in the user-specific information contained in the first database. In the user-specific information, the encryption key data is placed e.g. in a separate field or distributed in several fields, in which case the encryption key data can be retrieved using e.g. a predetermined algorithm. The user information does not necessarily contain the encryption key as such, but only an index pointing to it. The encryption key itself may be stored elsewhere.
According to the method, the encryption key in use in the telephone exchange system is changed. The encryption key to be changed does not necessarily cover the entire telephone exchange system, but it may also be user and/or group-specific. The next time when the user logs on in the system after the change, the encryption key used last as indicated by the user-specific information is compared with the present encryption key data of the telephone exchange system. In this comparison, the parties compared are e.g. the encryption key index in the user-specific information and the encryption key index in use. If these encryption key data items do not differ from each other, then the encryption key data in the user information and the current encryption key data in the telephone exchange system are identical. If the encryption key data items differ from each other, then the user is identified by the encrypted password which has been encrypted with the encryption key used last as indicated by the user information. The encryption key used last is not necessarily the key preceding the current encryption key, because the user may not have logged on in the system at all between the previous changes of encryption keys.
If the user is successfully identified, then the data indicating the encryption key used last in the first database is updated with the current encryption key data of the telephone exchange system. Correspondingly, the encrypted password contained in the user information is updated into a form consistent with the current encryption key.
The system of the invention comprises the necessary means for implementing the operations occasioned by the updating of the encryption key.
The invention makes it possible to update encrypted passwords automatically in conjunction with a change of the encryption key. Therefore, the passwords need not be updated manually by the operator or any other party. A normal user will not become aware of the updating of the encryption key at all. At the same time, system maintenance becomes easier as the change of the password does not impair the security of the system or affect its performance.